A Review paper on Routing Protocol Comparison Ms. Aastha kohli 1, Mr. Sukhbir 2 1 M.Tech(CSE) (N.C College of Engineering, Israna Panipat) 2 HOD Computer Science Dept.( N.C College of Engineering, Israna Panipat) ABSTRACT This paper presents a broad study on the work of common MANET (mobile adhoc network) routing protocols. The routing protocols used in this study include AODV, DSR and DSDV which consist of a mixture of reactive and proactive protocols. The paper is a survey of research on routing protocols for MANET. The paper has been made to compare three well know protocols AODV, DSR and DSDV by using three performance metrics packet delivery ratio, average end to end delay and routing overhead. The comparison has been done by using simulation tool NS2, NAM (Network Animator) and excel graph which is used for preparing the graphs from the trace files. Keywords: MANET, NS-2, AODV, DSDV, DSR 1. INTRODUCTION The routing protocol should be power-efficient. Mobile ad hoc networks (MANETs) are freely selforganized networks without infrastructure support. In a mobile ad hoc network, nodes move readily. Because nodes in a MANET normally have low transmission ranges, some nodes cannot communicate directly with each other. Hence, routing paths in mobile ad hoc networks potentially contain multiple hops, and every node in mobile adhoc networks has the responsibility to act as a router. Mobile Ad-hoc networks are selfconfigured multihop wireless networks where, the structure of the network changes dynamically. This is mainly due to the mobility of the nodes [2]. Nodes in these networks utilize the same random access wireless channel, cooperating in a friendly manner to engaging themselves in multihop forwarding. The node in the network not only acts as hosts but also as routers that route data to/from other nodes in network [1]. Some examples include interaction of students during lecture, sharing of files by business associates in an airport terminal. The group of mobile hosts may form their ad hoc network, if every mobile host is equipped with wireless local area network interface. The routing protocol should be secure. A hybrid routing protocol should be more reactive than proactive to avoid overhead. A routing protocol should qualify the Quality of Service (QoS) Wireless ad-hoc networks have got a lot of importance in wireless communications. Wireless communication is established by nodes acting as routers and transferring packets from one to another in ad-hoc networks. Routing in these networks is more complicated due to moving nodes and hence many protocols have been developed. In this paper we have selected three main routing protocols.figure1 below represents the scenario of MANET. Routing protocols of MANET should have the following Properties: A routing protocol should be assigned in manner in order to increase its reliability. Figure 1 Ad-hoc Network Architecture A routing protocol must be designed considering unidirectional links because wireless medium may cause a wireless link to be opened in unidirectional only due to physical factors. 2 Applications of MANET: MANETs are useful in places where no communication infrastructure or the infrastructure is damaged. Typical applications are: Page 29
Military or police exercises. Disaster relief operations. Mine cite operations. Urgent Business meetings. 3 Challenges of MANET: Finite wireless transmission range: In wireless networks the radio band will be limited and hence data rates it can offer are much lesser than what a wired network can offer. This requires the routing protocols in wireless networks to use the bandwidth always in an optimal manner by keeping the overhead as low as possible [3]. frequent path breaks due to mobility of nodes, and the inherent fading properties of the wireless channel [3]. 4 Classification of Adhoc Routing Protocol Routing protocol in MANET can be classified into several ways depending upon the network structure, communication model, routing Strategy, and state information and so on but most of these are done depending on routing strategy and network structure. Routing Overhead: In wireless adhoc networks, nodes are random they often change their location within network. Some weak routes are generated in the routing table which leads to unnecessary routing overhead. Battery constraints: This is one of the limited resources that form a major constraint for the nodes in an ad hoc network. Devices used in these networks have restrictions on the power source in order to maintain portability, size and weight of the device. By increasing the power and processing ability makes the nodes bulky and less portable. So only MANET nodes has to optimally use this resource [4]. Asymmetric links: Most of the wired networks rely on the symmetric links which are always fixed. But this is not a case with adhoc networks as the nodes are mobile and constantly changing their position within network. For example consider a MANET ( Mobile Ad-hoc Network) where node B sends a signal to node A but this does not tell anything about the quality of the connection in the reverse direction [5]. Time-varying wireless link characteristics: The wireless channel is susceptible to a variety of transmission impediments such as path loss, fading, interference and blockage. These factors resist the range, data rate, and the reliability of the wireless transmission. The extent to which these factors affect the transmission depends upon the environmental conditions and the mobility of the transmitter and receiver. Even the two different key constraints, Nyquist s and Shannon s theorems, that govern the ability to transmit information at different data rates can be considered [3]. Packet losses due to transmission errors: Ad hoc wireless networks experiences a much higher packet loss due to factors such as high bit error rate (BER) in the wireless channel, increased collisions due to the presence of hidden terminals, presence of interference, location dependent contention, uni-directional links, Figure 2 Classification of Adhoc Routing Protocol. 4.1 Destination-Sequenced Distance-Vector Routing (DSDV) DSDV is a hop to hop distance vector routing protocol. In this protocol, each node has a routing table that stores the next hop, number of hops for all the reachable destinations. Each node broadcast routing updates periodically. The advantage of DSDV over traditional distance vector routing protocols is that DSDV guarantees loop-free routing. Destination-Sequenced Distance- Vector Routing (DSDV) is a table -driven routing scheme for adhoc mobile networks based on the Bellman-Ford algorithm. It was developed by C. Perkins and P.Bhagwat in 1994. In DSDV, each node maintains a next-hop table, which it exchanges with its neighbors. There are two types of next-hop table exchanges: periodic fulltable broadcast and event-driven incremental updating. The relative frequency of the full-table broadcast and the incremental updating is determined by the node mobility. In each data packet sent during a next-hop table broadcast or incremental updating, the source node appends a sequence number. This sequence number is propagated by all nodes receiving the corresponding distance-vector updates, and is stored in the next-hop table entry of these nodes. A node, after receiving a new next-hop table from its neighbor, updates its route to a destination only if the new sequence number is larger than the recorded one, or if the new sequence number is the same as the recorded one, but the new route is shorter. In order to further reduce the control message overhead, a settling time is estimated for each route. A node updates to its neighbors with a new route only if the settling time of the route has expired and the route remains optimal [8]. Page 30
4.2 Dynamic Source Routing (DSR) The Dynamic Source Routing protocol (DSR) is (Perkins, 2007), an on demand routing protocol. DSR is a simple and efficient routing protocol designed specifically for use in multi-hop wireless ad hoc networks of mobile nodes. Using DSR, the network is completely self organizing and self-configuring, requiring no existing network infrastructure or administration. The DSR protocol is composed of two main mechanisms that work together to allow the discovery and maintenance of source routes in the ad hoc network [7]: Route Discovery is the mechanism by which a node S wishing to send a packet to a destination node D obtains a source route to D. 5.1 Simulation Tool In this paper the simulation tool used for analysis is NS-2 which is highly preferred by research communities. Software used for the performance analysis of taken protocol is based on NS-2 version 2.27. NS Simulator based on two languages: an object oriented simulator, written in C++, and OTcl (an object oriented extension of Tcl) interpreter, use to execute users command scripts. NS2 is an object oriented simulator, written in C++, with an OTcl interpreter as a frontend. This means that most of the simulation scripts are created in Tcl (Tool Command Language). If the components have to be developed for ns2, then both tcl and C++ have to be used. The flow diagram given in figure3 shows the complete structure of NS2. Route Discovery is used only when S attempts to send a packet to D and does not already know a route to D. Route Maintenance is the mechanism by which node S is able to detect, while using a source route to D, if the network topology has changed such that it can no longer use its route to D because a link along the route no longer works. When Route Maintenance indicates a source route is broken, S can attempt to use any other route it happens to know to D, or it can invoke Route Discovery again to find a new route for subsequent packets to D. Route Maintenance for this route is used only when S is actually sending packets to D. In DSR Route Discovery and Route Maintenance each operates entirely" on demand"[7]. 4.3 Ad hoc On-Demand Distance Vector (AODV) Routing Protocol The ad hoc on demand distance vector (AODV) routing protocol is a multi-hop routing protocol. It enables multi-hop routing between the nodes who wish to establish and maintain ad hoc network. It is based on distance vector routing algorithm. AODV allows mobile nodes to respond to link breakages and changes in network topology in a timely manner. The operation of AODV is loop-free, and by avoiding the Bellman-Ford counting to infinity" problem offers quick convergence when the adhoc network topology changes (typically, when a node moves in the network). When links break, AODV causes the affected set of nodes to be notified so that they are able to invalidate the routes using the lost link. Route Requests (RREQs), Route Replies (RREPs) and Route Errors (RERRs) are message types defined by AODV [6]. 5.2 Simulation parameters are as follows: Platform Windows XP NS version Ns allinone-2.26 Simulation time 200 s Number of nodes 50 Wireless Nodes Transmission Range 250 m Simulation Area size 500 x 500 m 5 Simulation Based Analysis using Network Simulator (NS-2) Simulation Setup (traffic scenario, Mobility model) performance metrics used and finally the performance of protocols is represented by using excel graph. Traffic Node Speed CBR(Constant Bit Rate) fixed to 20 m/s Page 31
Protocols DSR,AODV and DSDV Pause time 0, 20, 40, 80, 120, 160, 200 5.3 Simulation Results Figure6. Avg. end to end delay versus pause time for AODV, DSR and DSDV (Number of node = 50, Area space = 500m x 500m) Figure4. Routing overhead versus pause time for AODV, DSR and DSDV (Number of node = 50, Area space = 500m x 500m 7. Conclusion Here we analyzed the performance of different routing protocol done in the mentioned mobility and traffic pattern on different pause time. We analyzed that when pause time set to 0 each of the routing protocols obtained around 97% to 99% for packet delivery ratio except DSDV which obtained 76%. DSR and AODV reached approx 100% packet delivery ratio when pause time equal to 200 while DSDV obtained only approx 94% packet delivery ratio.dsr and DSDV has low and stable routing overhead as comparison to AODV that varies a lot. Avg. End to End delay of DSDV is very high for pause time 0 but it starts decreasing as pause time increases. DSR performs well as having low end to end delay. When we compare the three protocols in the analyzed scenario we found that overall performance of DSR is better than other two routing protocols. REFERENCES: Figure5. Packet delivery ratio versus pause time for AODV, DSR and DSDV(Number of node = 50, Area space = 500m x 500m) [1] Mehran Abolhasan, Tadeusz Wysocki, and Eryk Dutkiewicz. A review of routing protocols for mobile ad hoc networks. Technical report, Telecommunication and Information Research Institute, University of Wollongong,Wollongong, NSW 2522. Motorola Australia Research Centre, 12 Lord St., Botany, NSW 2525, Australia,2003. [2] Xiaoyan Hong, Kaixin Xu, and Mario Gerla. Scalable routing protocols for mobile ad hoc networks. 2002. Page 32
[3] C. Siva Ram Murthy and B. S. Manoj, Ad Hoc Wireless Networks, Architectures and Protocols, Second Edition, Low price Edition, Pearson Education, 2007. [4] International Journal of Computer Science & Engineering Survey (IJCSES) Vol.1, No.1, August 2010 ANALYZING THE MANET VARIATIONS, CHALLENGES, CAPACITY AND PROTOCOL ISSUES G. S.Mamatha1 and Dr. S. C. Sharma [5] Jochen Schiller. Mobile Communications. Addison-Wesley, 2000. [6] Mobile Ad Hoc Networking Working Group AODV, http://www.ietf.org/rfc/rfc3561.txt [7] Mobile Ad Hoc Networking Working Group DSR, http://www.ietf.org/rfc/rfc4728.txt. [8] Wireless Ad Hoc Networks Zygmunt J. Haas, Jing Deng, Ben Liang, Panagiotis Papadimitratos, and S. SajamaCornell University School of Electrical and Computer Engineering. Page 33